I'm getting tired of seeing this kind of thing. It was a map pack. The term DLC was coined by microsoft because it was a BIG DEAL that consoles could now download new content for games. Previously, console games were static, bugs remained bugs if they couldn't be fixed server side, and new content couldn't be added. This was a huge reasoning for why people argued PC gaming was superior to console gaming. The hard drives on the ps2, xbox 360, and ps3 were a big deal in the wake that they changed the way console games were distributed.
However, Valve is and always has been a PC gaming publisher. In the past, game updates and patches weren't referred to as DLC. They were referred to by what they were, patches and map packs, and get this kids; they were all free.
In fact, mods like Left 4 Dead were all free prior to the release of steam and CS 1.6. I guess I'm just getting old, but I remember a better age in gaming, were people weren't surprised off their ass because a map pack and a slight software update was free. It was business as usual. I would like to believe that it is in the tradition of valve's business model that this is why the L4D "DLC" was free.
It's getting harder and harder to find good third party mod developers that don't use steam to try to make a buck off their game. The original counter strike, TFC, DoD, Zombie Panic, and many many more mods were ALL free back in the day. They were all great games, and nobody was surprised they were free. Everyone once in a while, valve would buy the rights to one of the mods (as they did with TFC and CS) and sell them retail as a new release of half-life (ie. game of the year edition, platinum edition) but the mods still existed on the developer's website as free downloads. People released map packs, custom maps, and modifications to those mods all the time, no one ever charged.
Now every third party mod developer and their mom sell their mods via steam to try to turn a profit. It's getting harder and harder to find good third party mod developers who just program as a hobby, and for the love of gaming and programming. Don't get me wrong, steam is a great software distribution system. In fact, i'll go as far as to say it is the best online software distribution system out there. I really hope though it doesn't start turning into an xbox live arcade sort of deal where they start charging you for game updates. That's justa slap in the face to computer gamers everywhere. Sadly, I think that's where we see the future to be headed.
Thanks for reading my $.02